Mary Yellan arrives at the isolated Jamaica Inn to live with her aunt, only to discover the establishment serves as a front for a brutal gang of wreckers. Mary seeks refuge with her kin following her mother's death, but she finds her aunt living in terror under the control of her uncle, Joss Merlyn. The narrative follows Mary as she navigates the dangerous social and physical landscape of the Cornish moors, where the law is absent and the inn acts as a hub for criminal activity. The story is told through a third-person perspective that emphasizes the atmospheric tension of the coastal environment and the psychological isolation of the protagonist. Mary must determine who to trust as she becomes entangled in the illicit operations of the inn.

Readers frequently highlight the oppressive atmosphere and the vivid, bleak depiction of the Cornish coast as central to the book's effectiveness. Discussion often centers on the transformation of Mary Yellan from a vulnerable newcomer into a resilient figure capable of navigating extreme danger. Critics often note the balance between the slow-building suspense and the sudden, violent shifts in the narrative arc. Many readers appreciate the way the author avoids simplistic characterizations, instead presenting individuals with complex motivations and hidden agendas. The work is widely regarded for its ability to maintain a sense of dread throughout the entire narrative without relying on excessive action sequences.